how to unregister BaseAdapter that depends on other source

Question

I have a MyAdapter extends BaseAdapter that extract information from JniSource. MyAdapter implements JniSource.Observer and get a callback when underlying JNI data is changed.

My Question: I can JniSource.registerObserver(MyAdapter) in constructor but where to call JniSource.unregisterObserver(MyAdapter).

MyAdapter.finalize() cannot be the place because JniSource is still having reference (inside LinkedList) to MyAdapter. If I don't call JniSource.unregisterObserver() this would cause a leak.

Extra Note: all JniSource methods are static.

Answer 1

The idea is simple, when MyAdapter have observer, then MyAdapter register itself to the JniSource. using this way i do not have to mantain anything absolute. (life cycle is relative).

Added benifit: This also prevent from unwanted changed callback from JniSource since there are no observer for MyAdapter

public abstract class MyAdapter extends BaseAdapter implements JniSource.Observer {
    private int observer_count = 0;

    @Override
    public void registerDataSetObserver(DataSetObserver observer) {
        super.registerDataSetObserver(observer);
        if(observer_count == 0) {
            JniSource.registerObserver(this);
        }

        observer_count++;
    }

    @Override
    public void unregisterDataSetObserver(DataSetObserver observer) {
        super.unregisterDataSetObserver(observer);
        //FIXME: what if unregisterDataSetObserver got called for a non-registered observer?
        observer_count--;
        if(observer_count == 0) {
            JniSource.unregisterObserver(this);
        }
    }

    public void onJniSourceDataChanged() {
        notifyDataSetChanged();
    }
};